Comparison of pH-induced protein–polyphenol self-assembly methods: Binding mechanism, structure, and functional characteristics

Herein, we used pH-shifted and pH-driven methods to assemble kidney-bean protein isolate (KPI) and luteolin (Lut) into a nanocomplex and subsequently investigated their binding mechanism, structure, and functional properties. Results showed that the nanocomplex prepared by the pH-driven method exhibited a better encapsulation effect and controlled release of Lut. Fluorescence spectroscopy and molecular docking analysis showed that the binding affinities under alkaline conditions were higher than those under acidic and neutral conditions. Various spectral techniques were used to determine the structural changes in the KPI-Lut nanocomplex, including the transformation of α-helices and β-sheets and alteration of specific amino acid microenvironments, which were more pronounced in the pH-driven nanocomplex. The structural changes in the nanocomplex further affected their surface hydrophobicity and thermal stability. Additionally, the combination of KPI and Lut significantly improved the antioxidant activity and α-glucosidase inhibitory ability of the resultant nanocomplexes, particularly the one prepared by the pH-driven method.